Select between maximum runtime, long service life, small size and low cost.
Rechargeable batteries play an important role in our lives and many daily chores would be unthinkable without the ability to recharge an empty battery. As the battery improves, an increasing number of devices are fitted with rechargeable batteries. The points of interest are good runtimes, economical price, long life, large loading capabilities, safe operation, ease of storage and disposal.
The most common rechargeable batteries are Lead acid, NiCd, NiMH and Li-ion.
Battery research gravitates towards lead- and lithium-based batteries. AGM (Absorbent Glass Mat) is a major battery type in the lead acid family and lead acid with carbon additives are making progress by allowing faster charge and increasing cycle life. (See BU-202: New Lead Acid Systems). Lead acid is estimated to grow in market share, but the bulk of battery growth is with Li-ion. (See BU-204: How do Lithium Batteries Work?)
Table 1 compares the characteristics of the four commonly used rechargeable battery systems showing average performance ratings at time of publication. Li-ion is divided into many different types, each is described in more detail in BU-205: Types of Lithium-ion. The batteries are so named by their active materials that in most cases are the cathode. The traditional Li-ion systems are cobalt, manganese and phosphate.
Missing in the list is the popular lithium-ion-polymer. This battery gets its name from the unique separator and electrolyte system that energizes the battery. Once fully developed and refined, the polymer architecture has a large potential.
Also missing is the rechargeable lithium-metal. This battery is subject to more development in controlling dendrite growth, which can compromise safety. Once resolved, Li-metal has the prospect of becoming an alternative battery choice with extraordinary high specific energy and good specific power. Other promising lithium-based batteries are making advancements, albeit very incremental. These are described under BU-211: Alternative Battery Systems and BU-212: Experimental Rechargeable Batteries.
Unique packaging has made Li-ion available and affordable. The most common format is the 18650, a cell that measures 18mm in diameter and is 65mm long. This format offers the largest variety, highest specific energy, lowest cost per Wh and perhaps also provides the most reliable service. Over 2.5 billion 18650 cells have been produced in 2013. (See BU-301: A look at Old and New Battery Packaging.)
Three unique categories of Li-ion have emerged, each addressing different applications. Available in 18650 (and other formats) these categories are the Energy Cell energy with high capacity, the Power Cell with high loading capabilities and the Hybrid Cells that satisfies both requirements at compromised performance levels. Other cells are made for extended temperature range and extremely long cycle counts.
Table 1: Characteristics of commonly used rechargeable batteries. The figures are based on average ratings of commercial batteries at time of publication. Specialty batteries with above-average ratings are excluded.
Last updated 2015-08-14
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